(a) Field of the Invention
The present invention relates to a variant Ernostar type long focus lens system.
(B) Description of the Prior Art
As Ernostar type long focus lens systems, there have conventionally been known ones comprising four components of five elements, i.e., a first positive lens, a second cemented meniscus doublet lens, a third negative meniscus lens and a fourth positive lens. Such a type of lens systems have common drawbacks that aberrations are unavoidably aggravated by shortening overall lengths of the lens systems and that it is impossible to design the lens systems so as to have large aperture ratios.
In order to eliminate such drawbacks, there have also been designed variant Ernostar type long focus lens systems wherein the second lens component is separated into two meniscus lens elements. It is possible to design a long focus lens system having a large aperture ratio of F/2.8 and short in its overall length by separating the second lens component as is described above. However, this type of lens system has a focal length of 100 to 135 mm. Lens systems having a focal length of 180 mm to 200 mm heretofore known to the public are designed for a telephoto ratio of 1 to 1.2 and a rather long overall lengths.